The ecological factors which allow fusobacteria to colonize the gingival crevice of the human oral cavity have not been identified. Two phenomena--chemotactic response to amino acids or small molecules excreted by other bacteria and specific adherence to other bacteria already in the gingival crevice -- could foster colonization of the area by members of the genus Fusobacterium. It is the aim of this project to determine whether one or both of these processes can occur. Fusobacteria capable of independent growth will be isolated and identified by morphological and biochemical criteria. Similar strains whose growth is dependent on, or greatly enhanced by, the presence of a gram positive partner will also be isolated. The growth factor responsible for the interdependence of the pairs will be identified and supplied to the medium. Thereafter the strains will be cultivated separately and identified by standard methods. The ability to move by gliding on a solid substrate will be examined. Those strains shown to be motile will be tested for a chemotactic response fo fermentable amino acids and/or to small molecules excreted by the gram positive organism with which it was originally isolated. Strains isolated as a member of a pair will be tested for the ability to attach specifically to the other member of the pair. The molecular nature of the attachment sites on the cell surface will be determined.